The present invention generally relates to “active implantable medical devices” as defined by the 14 Jun. 1993 Directive 93/41/EEC of the Council of the European Communities. This definition includes cardiac pacemakers, cardiac resynchronization therapy devices and/or implantable cardioverter defibrillators for treatment of rhythm disorders. The definition also includes active devices (e.g., implanted or not) and active devices for purely diagnostic systems. The definition includes external systems for home monitoring of patients (e.g., implementing a remote access device which is activated at regular intervals, such as daily, to download the data collected by an implant and to send the data for analysis to a remote station).
The invention also or alternatively relates to the monitoring of patients with heart failure, or at risk of heart failure. Heart failure is a complex disease with various causes and effects, notably including mitral valve regurgitation, dilated cardiomyopathy and ischemia. These are evolutionary and harmful phenomena; it is important to assess and monitor over time (e.g., to issue early warnings in case of worsening trend).
The change can result from a phenomenon called “cardiac remodelling,” which can be defined as all heart changes in response to a disease and is usually associated with a worsening prognosis. This cardiac remodeling occurs over time by increasing the size of the left ventricle, with a worsening ejection fraction due to the decrease in contractility, and ultimately a decrease in cardiac output with serious consequences on the body by progression of heart failure.
With the help of alerts to worsening of the patient's condition, one can modify the configuration of a pacemaker. One example is to begin providing joint and permanent stimulation of the left and right ventricles to resynchronize the latter via a technique named CRT (Cardiac Resynchronization Therapy) or BVP (BiVentricular Pacing). Indeed, the beneficial effects provided by CRT therapy can lead, ultimately, to reassess the applied therapy and to again change the primitive configuration and setup of the resynchronizer.
The reference technique for the evaluation of the conditions listed above (valvular regurgitation, left ventricular dilatation, etc.) is the evaluation by echocardiography. This procedure traditionally must be carried out by a qualified practitioner and is traditionally time consuming and expensive, preventing the technique from being applied often.
Various techniques for automated monitoring and diagnosis have been proposed, including those presented in EP 1,867,360 A2 and its US counterpart US2007/0293736 (Sorin CRM S.A.S, previously known as ELA Medical), which offers cross various information from minute ventilation (“MV”), activity (“G” accelerometer), endocardial acceleration (EA) or intracardiac bioimpedance sensors. Analysis algorithms produce indicators of risk of cardiac decompensation, and cross analysis methods issue an early warning composite signal of preventive alert, on different levels, depending on the indicators produced by the algorithms.
U.S. 2007/043299 A1 describes a device implementing another technique, based on the cross-analysis of the peak-to-peak amplitude of the first peak of endocardial acceleration and of the heart rate, to assess the progress of heart failure in a patient implanted with the device.
These algorithms are effective in assessing the patient overall cardiac contractility and the more or less rapid deterioration of this contractility, corresponding to different levels of alert. However, they do not allow more specific assessment of the development or progression of certain specific pathologies such as those mentioned above (ischemia, regurgitation of the mitral valve, etc.). It would therefore be desirable to provide a device and method for monitoring and diagnosis which could be implemented in accordance with the patient's own condition (e.g., to deliver better or more specific alerts).